Trailer tow preserving battery charge circuit

ABSTRACT

A method and integrated circuit for preserving a battery&#39;s charge and protecting electrical devices is disclosed. A maximum and a minimum battery voltage value at the output port are stored in a memory. A steady state battery voltage at the output port is measured and stored in the memory. A processor compares the measured steady battery voltage value to the maximum and the minimum battery voltage values. If the measured steady state battery voltage value is greater than the maximum battery voltage value, an over voltage state is reported by the processor. If the measured steady state battery voltage value is less than the minimum battery voltage value, a low battery voltage state is reported by the processor.

CROSS-REFERENCE TO RELATED APPLICATIONS

Pursuant to 35 U.S.C. §121, this application is a divisional applicationof U.S. patent application Ser. No. 12/039,015, entitled “IntegratedCircuit and Method for Preserving Vehicle's Battery Charge andProtecting Trailer Load,” filed Feb. 28, 2008, which claims priorityfrom U.S. Provisional Patent Application Ser. No. 60/978,019, entitled“Smart Trailer Tow Connector,” filed Oct. 5, 2007, and U.S. ProvisionalPatent Application Ser. No. 60/920,465, entitled “Enhanced DynamicTrailer Detection, Exterior Lighting Classification and Short CircuitProtection Method, Improvement and Enhancement,” filed Mar. 27, 2007,and U.S. Provisional Patent Application Ser. No. 60/904,407, entitled“Enhanced Dynamic Trailer Detection, Exterior Lighting Classificationand Short Circuit Protection Method,” filed Feb. 28, 2007, thedisclosures of all of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The invention relates to electronic circuits, and more particularly theinvention relates to an integrated circuit and method for preserving avehicle's battery charge and for protecting electrical loads in atrailer attached to a tow vehicle.

BACKGROUND

In vehicles, aircraft, telecommunications and other systems, batteriesare often used to supply dc power to electrical devices (also referredto as electrical loads). The battery must be monitored to detect overvoltage and low voltage conditions. An over voltage condition may becaused by electrical transients such as an electrostatic discharge, acharging system load dump, electrical noise, electromagneticdisturbances or a vehicle jump start may damage attached electricalloads. A low voltage condition may be caused, for example, by a fault inan electrical load drawing excessive amount of current, thereby reducingthe battery's voltage. If a low voltage condition is detected, loadshedding may be initiated by selective removal of one or more electricalloads to prevent the battery from being completely discharged. If anover voltage condition is detected, the battery voltage may be reducedto protect the electrical loads or the load may be temporarilydisconnected from the vehicle battery.

In vehicles designed to tow trailers, a trailer tow connector and theelectrical components installed in the vehicle to control trailer loads,are typically used to deliver electrical power to the trailer and mayalso monitor and control various devices or loads installed in thetrailer. In production trailer tow designs, the electrical switchingdevices and circuit protection devices may be installed in severallocations in the vehicle and are wired to the passive trailer towconnector. The trailer tow connector generally includes one or moreoutput ports or pins adapted to deliver electrical power to the trailerdevices or loads. The devices may include running lights, brake lights,parking lights, electric brakes, trailer battery and turn signals.Selected output ports or pins in the trailer tow connector are usuallyconnected to a device that serves a particular purpose. For example,there may be an output port for operating the brake lights on thetrailer and another output port for operating the right-hand turn signaland yet another for operating the left-hand turn signal.

Typically, a dedicated switched battery output pin on the trailer towconnector is used to power trailer loads which may include a trailermounted battery or may directly power trailer mounted accessories. Thesetrailer mounted accessories typically include thefurnace/heater/refrigerator igniter circuits, the water system, a DC-ACinverter or trailer interior lighting. These trailer loads may be usedwhile the trailer is being towed or when the tow vehicle is stationary,such as at a rest area or parked overnight. Additionally, the chargingof the trailer battery is not controlled in production trailer towelectrical designs and a full charge current is constantly applied thatcan overheat and damage the trailer battery.

Existing trailer tow connectors with their supporting electronicswitching and fixed protection devices typically lack the capability tointelligently perform real time measurements of the battery voltage todetect over voltage and low battery voltage conditions. Consequently,existing trailer tow connectors lack the capability to intelligentlyinitiate load shedding to prevent complete depletion of the batterycharge and also to reduce the output voltage, current or power deliveredto prevent damage to the load. Furthermore, mechanical trailer towconnectors in use today include circuits that are powered by a vehiclebattery (or other switched voltage applied) whenever the vehicle isrunning (switched battery output), or when the tow vehicle's headlamps,brakes, or turn signal outputs are active. These circuits remain poweredeven if a trailer is not connected to the tow vehicle, which may resultin trailer tow connector reliability problems due to the voltage in theconnector and its exposure to environmental extremes. Due to the voltagein the trailer tow connector, output pin corrosion and dendrite growthare frequent and can lead to undetected trailer electrical malfunctions.

SUMMARY OF THE EMBODIMENTS

A method and integrated circuit for preserving a vehicle's batterycharge and protecting electrical devices is disclosed. The electricaldevices each receive power from an output port of a respective powercontrol circuit coupled to the battery. The method includes determininga maximum and a minimum battery voltage value at the output port andstoring the maximum and minimum battery voltage values in a memory. Themaximum and minimum battery voltage values are based on the hardwarecharacteristic of the electrical device and the battery-type.

The method includes measuring a steady state battery voltage at theoutput port and storing the measured steady state battery voltage valuein the memory. The method includes comparing, by a processor, themeasured steady battery voltage value to the maximum and the minimumbattery voltage values. If the measured steady state battery voltagevalue is greater than the maximum battery voltage value, an over voltagestate is reported by the processor. If the measured steady state batteryvoltage value is less than the minimum battery voltage value, a lowbattery voltage state is reported by the processor.

The method includes determining if the loads are attached to the outputports, and if no loads are detected then removing power from the outputports to reduce corrosion and dendrite growth on exposed connectorterminals. The method includes detecting if an auxiliary battery isattached and based on monitoring the discharge rate of the auxiliarybattery, implementing a multi-stepped PWM current recharge method toprolong the life of the auxiliary battery.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the features, example embodimentsand possible advantages of the present invention, reference is now madeto the detailed description of the invention along with the accompanyingfigures and in which:

FIG. 1A is a simplified diagram of a trailer tow connector;

FIG. 1B is a block diagram of an electronic circuit installed inside thetrailer tow connector;

FIG. 2 is an example embodiment of a circuit for preserving a vehicle'sbattery charge and protecting electrical loads in a trailer attached tothe vehicle;

FIG. 3 is a flow diagram of an exemplary method for preserving abattery's charge and protecting electrical loads powered by the battery;

FIG. 4 is a flow diagram of another exemplary method for preserving thebattery's charge; and

FIGS. 5A-5B illustrate a flow diagram of an exemplary method forrecharging a battery.

DETAILED DESCRIPTION OF THE INVENTION

This application incorporates by reference U.S. patent application Ser.No. 10/967,389 (Publication No. 2006/0085099 A1), entitled “Method andSystem for Driving a Vehicle Trailer Tow Connector,” filed Oct. 18,2004. This application also incorporates by reference U.S. patentapplication Ser. No. 12/038,936, entitled “Integrated Circuit and Methodfor Monitoring and Controlling Power and for Detecting Open Load State,”and U.S. patent application Ser. No. 12/039,065, entitled “IntegratedCircuit and Method for Classification of Electrical Devices and ShortCircuit Protection,” both filed on Feb. 28, 2008. This application alsoincorporates by reference U.S. patent application Ser. No. 12/850,152,entitled “Trailer Tow Method for Controlling Charging,” filed Aug. 4,2010.

FIG. 1A shows a trailer tow connector 104 that may be installed in avehicle designed to tow a trailer. The trailer tow connector 104includes an electronic circuit 108 shown in FIG. 1B. Although theelectronic circuit 108 is shown separately, it will be understood thatthe electronic circuit 108 typically resides inside (for example,encapsulated or housed within) the trailer tow connector 104. Theelectronic circuit 108 includes one or more electronic devices 112operable to deliver power to the devices in the trailer. The electroniccircuit 108 may be installed on a PC board 116, which is securelyinstalled and may be environmentally sealed inside the trailer towconnector 104. The electronic circuit 108 includes one or more outputports or pins 120 that are each connected to a particular device in thetrailer.

FIG. 2 illustrates an example implementation of a circuit 200 forpreserving a vehicle's battery charge and protecting electrical loads ina trailer attached to the vehicle. The circuit 200 may be implemented asan integrated circuit device fabricated on a semiconductor substrate.Alternatively, the circuit 200 may be implemented with discrete,stand-alone components. The circuit is powered from a power supply whichmay comprise, for example, the battery 202 of a vehicle within which thecircuit 200 and connector 104 is installed.

The circuit controls and regulates electrical power from a battery 202to one or more loads 240 and/or a trailer/auxiliary battery 241. Thebattery 202 may be a vehicle battery while the trailer battery 241 maybe installed in a trailer to power one or more devices in the trailer.The load may be a resistive, inductive, capacitive, a battery or anyother type of load installed in a trailer that is towed by a vehicle.For example, the load may be a trailer lighting load (LED, incandescent,Xenon, etc.) or a trailer battery, e.g., a load type. If the attachedload type has been classified or is known, an appropriate load controlstrategy may be implemented. For example, an incandescent load may beprotected by a closed loop PWM voltage control, while an LED load may beprotected by a closed loop PWM current control. It will be apparent tothose skilled in the art that the circuit 200 may be utilized inaircraft power systems, telecommunications, networking, wireless andother applications.

As will be subsequently explained in more detail, the circuit 200 isconfigured to intelligently monitor a vehicle's battery (i.e., battery202) to detect over voltage and low voltage conditions. Throughout thisdocument, the vehicle battery voltage may refer to the actual vehiclebattery voltage if the engine is not running or may refer to the vehiclecharging voltage (battery/alternator) if the engine is running. If anover voltage condition is detected, the circuit 200 intelligentlyreduces or removes voltage supplied from the battery 202 to protectelectrical loads. If a low voltage condition is detected, the circuit200 intelligently initiates load shedding to prevent the battery 202from being completely discharged.

The circuit 200 includes a processor 204 coupled to a memory 208. Theprocessor 204 may be one of several commercially availablemicrocontrollers programmed to execute data processing tasks. Inparticular, the processor 204 is configured to receive data from, andstore data in, the memory 208. The processor 204 performs a plurality ofmathematical and/or logical operations on data received from both thememory 208 and from other components of the circuit 200 by executing aplurality of instruction codes.

The circuit 200 includes a switched power control circuit 212electrically coupled to the processor 200. The switched power controlcircuit 212 controls the power delivered to one or more load(s) 240 inresponse to a power control signal 206 from the processor 204. Theload(s) 240 may be electrically coupled to the switched power controlcircuit 212 via an associated output port 242. The switched powercontrol circuit 212 may optionally provide a feedback signal 210 to theprocessor 204. The feedback signal 210 may include power control circuitstatus including open, short, mode or other device fault details, or mayprovide other operational information such as device configuration,programming or manufacturing data. In one example implementation, theswitched power control circuit 204 is a power semiconductor device suchas a power MOSFET or a power integrated base transistor capable ofdelivering controlled power to the load 240. In response to the powercontrol signal 206 from the processor 204, the duty cycle of the powercontrol circuit 212 is varied to regulate the amount of power deliveredto the load 240. In one example implementation, the power control signal206 is a pulse width modulated signal with a varied duty cycle tocontrol the ON and OFF times of the switched power control circuit 212.

The circuit 200 includes a current sense circuit 216 configured tomeasure the current flowing in the power control circuit 212 and beingdelivered to each of the loads 240. The current sense circuit 216 may beincorporated into the switched power control circuit 212. Alternatively,the current sense circuit 216 may be a separate, stand-alone circuitconfigured to measure the current flowing to the load(s) 240. Thecurrent sense circuit 216 measures the current flowing to a given load240 and provides a current sense signal 218 in response to the measuredcurrent. As will be subsequently discussed, if the measured current isless than a predetermined current value, the current sense signal 218may indicate an open circuit state. The predetermined current value maybe a minimum current threshold based on the hardware designcharacteristics of the load 240 and/or the output port 242 of thecircuit 200. If the measured current is more than a maximum currentthreshold, the current sense signal 218 may indicate a short circuitcondition, prompting the processor 204 to remove power from the load240.

In one example implementation, the current sense circuit 216 includes areference current generator 224 that generates a reference current. Thecurrent sense circuit 216 also includes a comparator circuit 228 thatcompares the measured current flowing to the load 240 to the referencecurrent, and responsive to the comparison generates the current sensesignal 218. The reference current may be the minimum current thresholdor any other selected current value. The current sense signal 218 mayindicate the operating condition at the output port 242 including anypossible malfunction as well as indicate the operating condition of theload 240. More specifically, the current sense signal 218 may indicatethe existence of an open circuit state at port 242, a short circuitstate at port 242, or that the load 240 is drawing normal current.

In one example implementation, if there are no attached loads, e.g., alltrailer connector outputs have detected an open circuit, the processor204 may turn off all power control circuits 212. The removal of powerfrom the trailer tow connector when a trailer plug is not inserted (noconnections) will prevent corrosion and dendrite growth that typicallyoccur when connectors with closely spaced terminals and an electricalpotential are exposed to temperature variations, humidity and saltspray. The corrosion of the trailer tow connector pins may lead tointermittent or total failure of trailer electrical connections. The useand protection of a hitch lighting device is also provided for since theopen detection limit (current value) would be less than the currentdrawn by any hitch lighting device. The described protection methods areapplicable to all attached loads, whether being in the form of a traileror a hitch lighting device.

In one example implementation, a counter circuit 248 may be used tovalidate an open circuit condition. This circuit 248 is optionallyincluded, or optionally considered. Signal 218 may be alternatively feddirectly to processor 204. Multiple samples of current are taken. Thecounter circuit 248 may be incremented by the signal 218 for eachsuccessive detected open circuit condition during the sampling period.When the count exceeds a maximum threshold, the counter circuit 248 mayprovide a valid open circuit state signal 250 to the processor 204. Thecounter circuit 248 will be reset in the absence of the detection of asuccessive open circuit condition (for example, within the samplingperiod). Responsive to the valid open circuit state signal 250 from thecounter circuit 248, the processor may detect and report a valid opencircuit state condition.

The circuit 200 includes a voltage sense circuit 220 configured tomeasure the voltage applied by the power control circuit 212 across theload 240. The voltage sense circuit 220 may be incorporated into theswitched power control circuit 212. Alternatively, the voltage sensecircuit 220 may be a separate, stand-alone circuit configured to measurethe voltage applied across the load 240. The voltage sense circuit 220measures the voltage across the load 240 and provides a voltage sensesignal 222 in response to the measured voltage. If the measured voltageis greater than a predetermined voltage value, the voltage sense signal222 may indicate an over voltage condition. Also, if the measuredvoltage is less than a predetermined voltage value, the voltage sensesignal 222 may indicate a low battery voltage at the battery 202.Responsive to a low battery voltage condition at the battery 202, theprocessor 204 may initiate load shedding by removing or reducing powerto the load 240 to preserve the battery 202's charge. Responsive to anover voltage condition, the processor 204 may decrease the voltage,current or power applied across the load 240 to prevent damage to theload by adjusting the duty cycle of the power control signal 206 andthus controlling operation of the circuit 212.

In one example implementation, the voltage sense circuit 220 includes areference voltage generator 232 that generates a reference voltagesignal. The voltage sense circuit 220 also includes a voltage comparatorcircuit 236 that compares the measured voltage across the load 240 tothe reference voltage, and responsive to the comparison generates thevoltage sense signal 222. In an alternative embodiment the voltage sensecircuit may include a voltage comparator circuit that compares themeasured voltage applied to the power control circuit 212 to thereference voltage, and responsive to the comparison generates thevoltage sense signal 222.

In one example implementation, a counter circuit 252 may be used tovalidate an over voltage condition, an open condition or a low batteryvoltage condition. This circuit 252 is optionally included, oroptionally considered. Signal 222 may be alternatively fed directly toprocessor 204. Multiple samples of voltage are taken by circuit 220 withcorresponding multiple signals 222 being generated. The counter circuit252 may be incremented by the signal 222 for each successive detectedover voltage condition during the sampling period. When the countexceeds a maximum threshold, the counter circuit 252 may provide a validover voltage state signal 256 to the processor 204. The counter circuit252 will be reset in the absence of the detection of a successive overvoltage condition (for example, within the sampling period). Responsiveto the valid over voltage signal, the processor 204 may detect andreport an over voltage condition. A separate counter circuit (not shownin FIG. 2 but similar in configuration and connection to circuit 220)may be used to validate a low battery voltage condition or an opencondition.

In one example implementation, the circuit 200 includes a networkinterface circuit 244 for facilitating communication between theprocessor 204 and external devices (not shown in FIG. 2). For example,the network interface circuit 244 may facilitate communication between avehicle (not shown in FIG. 2) and a trailer tow connector incorporatingthe circuit 200. This interface allows the processor 204 to outputcommunications, such as detections of open load, short circuit or overvoltage conditions at the ports 242 and loads 240, to other devices andsystems. The interface further allows the processor 204 to receiveinformation, such as programming, command and control information, fromother devices and systems.

FIG. 3 is a flow diagram 300 of an exemplary method for preserving thecharge on battery 202 and protecting electrical devices or loads poweredby the battery 202. The method of FIG. 3 may be performed by the circuit200 shown in FIG. 2. The electrical devices may each receive power froman output port of a respective power control circuit such as the powercontrol circuit 212 shown in FIG. 2.

As discussed before, the circuit 200 may be incorporated in a trailertow connector for intelligently preserving the battery 202's charge andfor load shedding. It will be apparent to those skilled in the art, thatthe method illustrated in the flow diagram 300 can be utilized inaircraft power systems, telecommunications, wireless, networking andother applications.

In step 304, a maximum battery voltage value for the output port 242 isdetermined. The maximum battery voltage at the output port 242 dependson the rating and other design characteristics of the battery 202 aswell as the maximum voltage rating of the load attached to the outputport 242. This value could be programmed into the circuit throughinterface 244, or determined by the circuit 200 itself. In step 308, themaximum battery voltage value is stored in a memory such as the memory208. In step 312, the steady state voltage at the output port 242 ismeasured by the voltage sense circuit 220. In step 316, the measuredsteady state voltage is stored in the memory 208.

In step 320, the measured steady state voltage is compared to themaximum battery voltage. In one implementation, the processor 204compares the measured steady state voltage to the maximum batteryvoltage. If the measured steady state battery voltage is greater thanthe maximum battery voltage, an over voltage state or condition isreported in step 324. Otherwise, the flow returns to step 312.

In one implementation, the processor 204 reports the over voltage statevia the network interface 244. Responsive to the over voltage state, theprocessor 204 sends the power control signal 206 to adjust the voltageat the output port 242. In one implementation, the power control signal206 is a pulse width modulated signal that reduces the duty cycle of thepower control circuit 212 to reduce the voltage at the output port 242.The voltage at the output port 242 may be adjusted based on the type ofload coupled to the output port 242. In one implementation, theload-type is determined (e.g., incandescent bulb, gas discharge bulb,LED, battery) and based on the load-type, the power control signal 206is generated to adjust the output voltage, current or power to anappropriate level. The output voltage may be varied within a wide rangeof values, from a zero voltage to a maximum voltage. The current orpower measured in the load can also be varied within a selected range ofvalues. The power calculation can be based on the power delivered to theload or the power dissipated across the load. The foregoing analysis canbe made by the processor 204 with respect to each of the output ports242 coupled to a respective load 240. For example, to extend theoperational life of trailer incandescent lighting (bulbs), a closed loopvoltage PWM control implemented by the processor 204 and the powercontrol circuit 212, may be used to regulate the load voltage 242 tomaintain a constant 11.9V measurement under all conditions.

In one implementation, the duty cycle of the power control circuit 212is varied depending on the configuration of the circuit 212. If, forexample, the power control circuit 212 is configured as an open loopsystem, the duty cycle is adjusted to a pre-selected value (e.g., 0.7 or0.5). In contrast, if the power control circuit 212 is configured as aclosed loop system, the duty cycle is varied until the voltage at theoutput port is brought to a desired voltage level.

As discussed before, in order to preserve the charge on battery 202 itis necessary to monitor the voltage at the output port 242. A lowvoltage condition at the output port 242 may indicate that the battery'selectrical charge is low, thus requiring a load shedding to preserve thebattery's charge. FIG. 4 is a flow diagram 400 of an exemplary methodfor preserving the battery 202's charge. In step 404, a minimum batteryvoltage is determined. The minimum battery voltage value is a thresholdbelow which the battery is considered to be at risk of being depletedand where it would not be possible to start the vehicle. The minimumbattery voltage is based on the characteristics of the battery as wellas the load connected to the output port 242.

In step 408, the minimum battery voltage value is stored in the memory208. This value could be programmed into the circuit through interface244, or determined by the circuit 200 itself. In step 412, the steadystate voltage at the output port 242 is measured by the voltage sensecircuit 220. In step 416, the measured steady state voltage is stored inthe memory. In one implementation, the measured steady state voltage isstored in the memory 208 by the processor 204.

In step 420, the measured steady state voltage is compared to theminimum battery voltage. In one implementation, the processor 204compares the measured steady state voltage to the minimum batteryvoltage. In step 424, if the measured steady state voltage is less thanthe minimum battery voltage, a low battery voltage state is reported bythe processor 204. Otherwise, the flow returns to step 412. In responseto the low battery voltage state, the processor 204 sends the powercontrol signal 206 to vary the voltage at the output port 242. Forexample, the duty cycle of the power control circuit 212 may be reducedto decrease the voltage at the output port 242 to preserve the batterycharge. If necessary, the voltage at the output port 242 may be reducedto zero to remove power from the attached load 240.

In one example implementation, if a plurality of loads 240 are poweredby the battery 202, selective load shedding may be initiated to preservethe battery's charge. For example, if three loads are each coupled to arespective power control circuit, the duty cycle of each of the powercontrol circuits may be varied to reduce the respective voltage, currentor power across each load. In one implementation, if the load isconsidered a non-critical load, the duty cycle may be varied or thepower control circuit 212 may be disabled or turned off to removeelectrical power from the load. If the load is considered a criticalload, the duty cycle may be varied to reduce power at the output port inorder to decrease the rate of depletion of the battery's charge whileproviding an acceptable reduced voltage, current or power level to thecritical load. A critical load may, for example, be a load that impactsthe safety or operation of either the tow vehicle or the attached load.Examples of critical loads include running/marker and stop/brake lamps.An example of a non-critical load includes a switched battery outputthat powers trailer auxiliary loads. Data regarding critical andnon-critical loads may be stored in the memory 208 and accessed by theprocessor 204 for analysis.

A variety of load shed designs or strategies may be realized byimplementing logic on the processor 204 and utilizing measured data suchas the load voltage, the load current as well as vehicle operationalinformation that may be acquired through the network interface 244. Inone implementation, a vehicle battery's charge may be preserved by usingthe above-described method if the vehicle engine's RPM falls below a lowthreshold value and/or the vehicle speed is at or near zero MPH.Information regarding the vehicle's engine RPM or speed may be providedto the processor via the communication network interface 244. If thevehicle's engine RPM and speed falls below a predetermined or calculatedthreshold value, indicating the vehicle may be in an idle mode, one ormore loads may be disconnected from the battery. Consider for examplethat a vehicle's battery powers one or more loads installed in a trailerattached to the vehicle. If the vehicle is idling, i.e., in an idlemode, it may be unnecessary to power all the loads in the trailer.Accordingly, the vehicle engine's RPM and/or vehicle speed may bemonitored and measured, and responsive to the measurements, loadshedding may be initiated using the circuit 200 to preserve thebattery's charge. In addition to preserving the vehicle's batterycharge, idle mode load shedding can improve idle quality, fuel economyand vehicle acceleration/performance. Once vehicle speed, batteryvoltage or engine RPM have exceeded predetermined or calculatedrespective thresholds as stored in memory 208, the circuit 200 mayre-enable, turn on, or return to normal PWM control all power controlcircuits 212 that had been previously modified in the load shed action.In one example implementation, load shedding can be applied selectivelyto critical loads based on operating conditions. For example ifheadlamps are on and it is daytime (as sensed by an ambient light signaltypically used with an auto-headlamps feature and provided throughinterface 244), then it would be permissible and safe to perform atleast a minimum load shed on the trailer marker/running lamps.Additional vehicle status information (provided through interface 244)such as fog lamps status or wiper status can be used as additionalfactors considered by the logic to control the load shed function. Inone implementation, if it is daytime (ambient light sensor=daytime) andit is foggy outside (fog lamps=on), then load shedding of trailermarker/running lights will not be initiated (because these lights areconsidered safety important).

In one implementation, if the vehicle is in a sleep mode (e.g., vehicleengine turned off, vehicle door or headlamp switches not activated asknown from the information communicated on the interface 244) or thenetwork interface 244 is in a sleep state, electrical power may beremoved from one or more loads to preserve the battery's charge. Forexample, in response to a determination that the vehicle is in a sleepmode, load shedding may be initiated to disconnect power from one ormore attached trailer loads to preserve the battery's charge. Thevehicle may provide a signal to the processor 204 via the networkinterface 244 indicating that the vehicle is in a sleep mode.

In one implementation, the circuit 200 can be utilized to preserve thebattery's charge in response to a thermal overload (i.e., over heating)condition as sensed internally by the circuit 200. Thus, the circuit 200may be configured to measure the temperature of the loads 240 andprovide a temperature sense signal (e.g., signal 210 or communicatedthrough interface 244 or some other received signal) responsive to themeasured load temperature. The temperature sense signal isrepresentative of the load temperature. A thermal overload condition mayindicate that the load 240 is drawing excessive current, thusnecessitating load shedding to prevent a permanent malfunction ordegradation resulting from continued thermal overstress or fast thermaltransients. For example, if the temperature sense signal indicates thatthe load temperature exceeds a maximum temperature threshold, loadshedding may be initiated using the above-described method. The thermaloverload condition at load 240 may be communicated to processor 204 viathe signal 210 from the power control circuit 212. Alternatively, one ormore temperature sensing devices may be installed on a trailer towconnector PCB board whose signals may be connected to the processor 204.

In one implementation, the circuit 200 may be utilized to recharge atrailer battery 241 that is electrically coupled to a vehicle batteryvia the circuit 200. The trailer battery is generally installed incertain trailer types (RV or commercial) that can be towed by a vehicle.The trailer battery may power one or more loads installed in the trailersuch as interior trailer lights, a trailer DC-AC inverter, orfurnace/heater/refrigerator natural gas igniter circuits.

FIGS. 5A-5B illustrate a flow diagram 500 of an exemplary method forrecharging a trailer battery (e.g., battery 241) using the circuit 200.In step 504, a determination is made if a trailer battery 241 iselectrically coupled to the vehicle battery (this can be accomplishedthrough current and/or voltage sensing). In step 508, a trailer batterypresent status is reported if a trailer battery 241 is coupled to thevehicle battery. In step 512, a maximum trailer battery recharge rate isdetermined. The maximum trailer battery recharge rate is the maximumpermissible vehicle charging rate of the trailer battery and is based onthe characteristic of the detected trailer battery. This value can becalculated, or loaded through the interface 244. In step 516, themaximum trailer battery recharge rate value is stored in the memory 208.In step 520, a steady state trailer battery discharge rate is measured.The steady state trailer battery discharge rate depends on one or moreloads attached to the trailer battery as well as the state of charge orcondition of the trailer battery. In step 524, the measured steady statetrailer battery discharge rate is stored in the memory 208. In step 528,the measured discharge rate is compared to the maximum recharge rate. Ifthe measured discharge rate exceeds the maximum recharge rate, in step532 the duty cycle of the power control circuit 212 is varied torecharge the trailer battery. Otherwise, the flow returns to step 520.

In one implementation, the processor 204 sends a first power controlsignal 206 to recharge the trailer battery at a high rate during a firsttime period and then at a low rate during a second time period. Thetrailer battery may alternately be recharged at a high rate and a lowrate until the trailer battery is completely recharged. By alternatelyrecharging the trailer battery at a high and a low rate, the operationallife of the trailer battery is prolonged. The charging time at both thehigh and low recharge rates are calculated based on the measured trailerbattery discharge rate.

The foregoing methods allows intelligent load shedding by preserving avehicle's battery charge, which allows the driver to return the vehiclehome, to a service station or other safe location. These methods providefor increased electrical efficiency, which can lead to improved fueleconomy, improved idle quality and improved vehicle acceleration andperformance.

It will also be appreciated that one or more of the elements depicted inthe drawings/figures can also be implemented in a more separated orintegrated manner, or even removed or rendered as inoperable in certaincases, as is useful in accordance with a particular application. It isalso within the spirit and scope of the present invention to implement aprogram or code that can be stored in a machine-readable medium topermit a computer to perform any of the methods described above.

As used in the description herein and throughout the claims that follow,“a”, “an”, and “the” includes plural references unless the contextclearly dictates otherwise. Also, as used in the description herein andthroughout the claims that follow, the meaning of “in” includes “in” and“on” unless the context clearly dictates otherwise.

The foregoing description of illustrated embodiments of the presentinvention, including what is described in the Abstract, is not intendedto be exhaustive or to limit the invention to the precise formsdisclosed herein. While specific embodiments of, and examples for, theinvention are described herein for illustrative purposes only, variousequivalent modifications are possible within the spirit and scope of thepresent invention, as those skilled in the relevant art will recognizeand appreciate. As indicated, these modifications may be made to thepresent invention in light of the foregoing description of illustratedembodiments of the present invention and are to be included within thespirit and scope of the present invention.

Thus, while the present invention has been described herein withreference to particular embodiments thereof, a latitude of modification,various changes and substitutions are intended in the foregoingdisclosures, and it will be appreciated that in some instances somefeatures of embodiments of the invention will be employed without acorresponding use of other features without departing from the scope andspirit of the invention as set forth. Therefore, many modifications maybe made to adapt a particular situation or material to the essentialscope and spirit of the present invention. It is intended that theinvention not be limited to the particular terms used in followingclaims and/or to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include any and all embodiments and equivalents falling within thescope of the appended claims. Thus, the scope of the invention is to bedetermined solely by the appended claims.

1. An integrated circuit device for preserving a battery's charge andprotecting electrical devices, the integrated circuit comprising: amemory; a processor electrically coupled to the memory; a power controlcircuit electrically coupled to the electrical device, the power controlcircuit operable to control electrical power delivered to the electricaldevice responsive to a power control signal from the processor; and avoltage sense circuit electrically coupled to the power control circuit,the voltage sense circuit operable to measure voltage at an output portof the power control circuit and to provide to the processor a voltagesense signal representative of the measured voltage; wherein theprocessor is operable to provide the power control signal to the powercontrol circuit responsive to the voltage sense signal, compare themeasured voltage to a reference voltage, and to report an error stateresponsive to the comparison.
 2. The integrated circuit device of claim1, wherein the processor is operable to control the power controlcircuit to adjust the voltage, current, or power at the output portresponsive to the error state.
 3. The integrated circuit device of claim1, further comprising a validation circuit operable to determine thatthe error state is valid or invalid, the processor further operable toignore the error state based on the determination.
 4. The integratedcircuit device of claim 1, wherein the reference voltage is a highbattery voltage, and the error state is an over voltage state when themeasured voltage exceeds the high battery voltage.
 5. The integratedcircuit device of claim 1, wherein the reference voltage is a lowbattery voltage, and the error state is a low battery voltage state whenthe measured voltage is less than the low battery voltage.
 6. Theintegrated circuit device of claim 1, wherein the processor is furtheroperable to determine a load type of the electrical device and controlthe power control circuit to adjust voltage, current, or power at theoutput port based on the load type of the electrical device.
 7. Theintegrated circuit device of claim 1, wherein the power control circuit,the processor and the memory are implemented in a trailer tow connectorconfigured to regulate power in one or more electrical devices installedin a trailer attached to a vehicle.
 8. The integrated circuit device ofclaim 7, wherein the processor is further operable to determine if thetrailer is attached to the vehicle, and control the power controlcircuit to reduce the voltage, current, or power from one or more outputports when the trailer is not attached to the vehicle.
 9. The integratedcircuit device of claim 1, further comprising a network interfacecircuit operable to facilitate communication between the processor andexternal devices.
 10. The integrated circuit device of claim 9, whereinthe power control circuit, the processor, and the memory are implementedin a trailer tow connector configured to regulate power in one or moreelectrical devices installed in a trailer attached to a vehicle, thenetwork interface further operable to provide vehicle operatingconditions to the processor.
 11. The integrated circuit device of claim10, wherein the processor is operable to control the power controlcircuit to adjust the voltage, current, or power at the output portbased on the vehicle operating conditions.
 12. The integrated circuitdevice of claim 1, wherein the power control signal is a pulse widthmodulated signal, and the power control circuit is a switched powercontrol circuit operable to control the electrical power delivered tothe electrical device by varying a duty cycle responsive to the powercontrol signal.
 13. The integrated circuit device of claim 12, whereinthe switched power control circuit is configured as an open loop system,and the power control signal varies the duty cycle of the switched powercontrol circuit to a pre-selected first duty cycle.
 14. The integratedcircuit device of claim 12, wherein the switched power control circuitis configured as a closed loop system, and the power control signalvaries the duty cycle of the switched power control circuit until thevoltage at the electrical device is equal to a pre-selected firstvoltage.
 15. An integrated circuit device for preserving a battery'scharge and protecting electrical devices, the integrated circuitcomprising: a memory; a processor electrically coupled to the memory; apower control circuit electrically coupled to the electrical device, thepower control circuit operable to control electrical power delivered tothe electrical device responsive to a power control signal from theprocessor; and a current sense circuit electrically coupled to measurecurrent flowing to an output port of the power control circuit andoperable to provide to the processor a current sense signalrepresentative of the measured current; wherein the processor isoperable to provide the power control signal to the power controlcircuit responsive to the current sense signal, compare the measuredcurrent to a reference current and to report an error state responsiveto the comparison.
 16. The integrated circuit device of claim 15,further comprising a validation circuit operable to determine that theerror state is valid or invalid, the processor further operable toignore the error state based on the determination.
 17. The integratedcircuit device of claim 15, wherein the processor is further operable tocontrol the power control circuit to reduce voltage, current, or powerat the output port responsive to the error state.
 18. The integratedcircuit device of claim 15, wherein the processor is further operable todetermine a load type of the electrical device and control the powercontrol circuit to adjust voltage, current, or power at the output portbased on the load type of the electrical device.
 19. The integratedcircuit device of claim 15, wherein the power control circuit, theprocessor and the memory are implemented in a trailer tow connectorconfigured to regulate power in one or more electrical devices installedin a trailer attached to a vehicle.
 20. The integrated circuit device ofclaim 19, wherein the processor is further operable to determine if thetrailer is attached to the vehicle, and control the power controlcircuit to reduce the voltage, current, or power from one or more outputports when the trailer is not attached to the vehicle.
 21. Theintegrated circuit device of claim 15, further comprising a networkinterface circuit operable to facilitate communication between theprocessor and external devices.
 22. The integrated circuit device ofclaim 21, wherein the power control circuit, the processor, and thememory are implemented in a trailer tow connector configured to regulatepower in one or more electrical devices installed in a trailer attachedto a vehicle, the network interface further operable to provide vehicleoperating conditions to the processor.
 23. The integrated circuit deviceof claim 22, wherein the processor is operable to control the powercontrol circuit to adjust the voltage, current, or power at the outputport based on the vehicle operating conditions.
 24. The integratedcircuit device of claim 15, wherein the power control signal is a pulsewidth modulated signal, and the power control circuit is a switchedpower control circuit operable to control the electrical power deliveredto the electrical device by varying a duty cycle responsive to the powercontrol signal.
 25. The integrated circuit device of claim 24, whereinthe switched power control circuit is configured as an open loop system,and the power control signal varies the duty cycle of the switched powercontrol circuit to a pre-selected first duty cycle.
 26. The integratedcircuit device of claim 24, wherein the switched power control circuitis configured as a closed loop system, and the power control signalvaries the duty cycle of the switched power control circuit until thecurrent flowing in an electrical device is equal to a pre-selected firstcurrent.
 27. The integrated circuit device of claim 15, wherein thereference current is a low current threshold, and the error state is anopen circuit state when the measured current is less than the lowcurrent threshold.
 28. The integrated circuit device of claim 15,wherein the reference current is a high current threshold, and the errorstate is a short circuit state when the measured current exceeds thehigh current threshold.
 29. A trailer tow connector configured topreserve a battery's charge and regulate power in one or more electricaldevices installed in a trailer attached to a vehicle, the trailer towconnector comprising: a memory; a processor electrically coupled to thememory; a power control circuit electrically coupled to the electricaldevice, the power control circuit operable to control electrical powerdelivered to the electrical device responsive to a power control signalfrom the processor; and sensing circuitry electrically coupled tomeasure at least one of voltage, current, or power at an output port ofthe power control circuit and operable to provide to the processor asensing signal representative of the measured voltage, current, orpower; wherein the processor is operable to provide the power controlsignal to the power control circuit responsive to the sensing signal.30. The trailer tow connector of claim 29, wherein the processor isfurther operable to determine if the trailer is attached to the vehicle,and control the power control circuit to reduce the voltage, current, orpower at the output port if the trailer is not attached to the vehicle.31. The trailer tow connector of claim 29, wherein the processor isfurther operable to determine a load type of the electrical device andcontrol the power control circuit to adjust voltage, current, or powerat the output port based on the load type.
 32. The trailer tow connectorof claim 29, wherein the processor is further operable to compare themeasured voltage, current, or power to a reference signal, and report anerror state based on the comparison.
 33. The trailer tow connector ofclaim 32, wherein the processor is operable to control the power controlcircuit to adjust the voltage, current, or power at the output portresponsive to the error state.
 34. The trailer tow connector of claim32, further comprising a validation circuit operable to determine thatthe error state is valid or invalid, the processor further operable toignore the error state based on the determination.
 35. The trailer towconnector of claim 32, wherein the reference signal is a high batteryvoltage, and the error state is an over voltage state when the measuredvoltage exceeds the high battery voltage.
 36. The trailer tow connectorof claim 32, wherein the reference signal is a low battery voltage, andthe error state is a low battery voltage state when the measured voltageis less than the low battery voltage.
 37. The trailer tow connector ofclaim 32, wherein the reference signal is a low current threshold, andthe error state is an open circuit state when the measured current isless than the low current threshold.
 38. The trailer tow connector ofclaim 32, wherein the reference signal is a high current threshold, andthe error state is a short circuit state when the measured currentexceeds the high current threshold.
 39. The trailer tow connector ofclaim 29, wherein the power control signal is a pulse width modulatedsignal, and the power control circuit is a switched power controlcircuit operable to control the electrical power delivered to theelectrical device by varying a duty cycle responsive to the powercontrol signal.
 40. The trailer tow connector of claim 39, wherein theswitched power control circuit is configured as an open loop system, andthe power control signal varies the duty cycle of the switched powercontrol circuit to a pre-selected first duty cycle.
 41. The trailer towconnector of claim 39, wherein the switched power control circuit isconfigured as a closed loop system, and the power control signal variesthe duty cycle of the switched power control circuit until the currentflowing in an electrical device is equal to a pre-selected firstcurrent.
 42. The trailer tow connector of claim 29, further comprising anetwork interface circuit operable to facilitate communication betweenthe processor and external devices.
 43. The trailer tow connector ofclaim 42, wherein the network interface is further operable to providevehicle operating conditions to the processor, and the processor isfurther operable to control the power control circuit to adjust thevoltage, current, or power at the output port based on the vehicleoperating conditions.
 44. An integrated circuit device for preserving abattery's charge and protecting an electrical device, the integratedcircuit comprising: a power control circuit electrically coupled to theelectrical device, the power control circuit operable, in response to apower control signal received from a processor, to control electricalpower delivered to the electrical device; and sensing circuitry operableto measure at least one of voltage, current, or power at an output portof the power control circuit and to provide, to the processor, a sensingsignal representative of the measured voltage, current, or power;wherein the power control signal is received from the processor inresponse to the sensing signal.
 45. The integrated circuit of claim 44,wherein the power control circuit is implemented in a trailer towconnector configured to regulate power in one or more electrical devicesinstalled in a trailer attached to a vehicle.
 46. The integrated circuitof claim 45, wherein the power control circuit is further operable toreduce the voltage, current, or power at the output port if the traileris not attached to the vehicle.
 47. The integrated circuit of claim 44,wherein the power control circuit is further operable to adjust voltage,current, or power at the output port based on a load type of theelectrical device.
 48. The integrated circuit of claim 44, wherein theprocessor is further operable to compare the measured voltage, current,or power to a reference signal, and report an error state based on thecomparison.
 49. The integrated circuit of claim 48, wherein the powercontrol circuit is operable to adjust the voltage, current, or power atthe output port responsive to the error state.
 50. The integratedcircuit of claim 48, further comprising a validation circuit operable todetermine that the error state is valid or invalid.
 51. The integratedcircuit of claim 48, wherein the reference signal is a high batteryvoltage, and the error state is an over voltage state when the measuredvoltage exceeds the high battery voltage.
 52. The integrated circuit ofclaim 48, wherein the reference signal is a low battery voltage, and theerror state is a low battery voltage state when the measured voltage isless than the low battery voltage.
 53. The integrated circuit of claim48, wherein the reference signal is a low current threshold, and theerror state is an open circuit state when the measured current is lessthan the low current threshold.
 54. The integrated circuit of claim 48,wherein the reference signal is a high current threshold, and the errorstate is a short circuit state when the measured current exceeds thehigh current threshold.
 55. The integrated circuit of claim 44, whereinthe power control signal is a pulse width modulated signal, and thepower control circuit is a switched power control circuit operable tocontrol the electrical power delivered to the electrical device byvarying a duty cycle responsive to the power control signal.
 56. Theintegrated circuit of claim 55, wherein the switched power controlcircuit is configured as an open loop system, and the power controlsignal varies the duty cycle of the switched power control circuit to apre-selected first duty cycle.
 57. The integrated circuit of claim 55,wherein the switched power control circuit is configured as a closedloop system, and the power control signal varies the duty cycle of theswitched power control circuit until the current flowing in theelectrical device is equal to a pre-selected first current.
 58. Theintegrated circuit of claim 44, further comprising a network interfacecircuit operable to facilitate communication between the processor andexternal devices.
 59. The integrated circuit of claim 58, wherein thenetwork interface is further operable to provide vehicle operatingconditions to the processor, and the power control circuit is operableto adjust the voltage, current, or power at the output port based on thevehicle operating conditions.